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February 2, 2026

Social Sign-In For Faster, Safer Access

Challenge	Approach	Results
Members returning on mobile in time-sensitive moments, often on unstable networks Too many hops between app, SMS, and email during sign in Members unsure which login path they used last time, increasing duplicate account risk	Introduce social sign in via a managed OAuth provider Meet members where they are with “Continue with Google/Apple” on the first screen Treat Google and Apple as additional credentials on one underlying identity	Less confusion and fewer duplicate accounts for members 6% increase in successful login completions after rollout 31% of logins this week going through the social sign in flow A reusable pattern other teams can adopt

Why We Wrote This

This post documents how we approached social sign in for SoLo Funds, a community finance marketplace where access speed matters.

Many of our members return to SoLo from their phones in time-sensitive situations, often on unstable networks and older devices. We saw that even small bits of friction – switching to SMS, waiting for an email, re-entering codes – could lead to dropped sessions right when access mattered most.

We wanted to:

• Make it faster and simpler for members to get back to their accounts
• Preserve the integrity of our account model and risk posture
• Avoid building a one-off solution that would be hard to extend to new providers

Rather than walk through implementation details, this post focuses on the design patterns we landed on, patterns that should translate to most modern web and mobile stacks.

Why Add Social Sign In At All?

For many consumer and fintech apps, social sign in needs to support a few common goals:

• Reduce time-to-access for returning users, especially on mobile
• Lower cognitive load by letting people reuse an identity they already trust
• Keep the security posture strong by layering social sign in on top of an existing account model, not replacing it

In our case at SoLo Funds, these goals mapped directly onto urgent, mobile use cases in a community finance marketplace, but the same motivations show up in many products with frequent, repeat sign ins.

The core idea we optimized for is simple:

Social sign in should be another way to authenticate the same underlying user, not a parallel account system.

The rest of this post unpacks what that means in practice.

What This Feels Like For A SoLo Member

On a typical day, a member might:

1. Open the SoLo app on their phone.
2. Tap “Continue with Google” or “Continue with Apple” on the first screen.
3. Approve with Face ID, Touch ID, or their device PIN.
4. Land back on the SoLo home screen in a few seconds, ready to continue where they left off.

They do not have to:

• Remember which email or password they used last time
• Wait for an SMS code or email link
• Worry about accidentally creating a second SoLo account

From their perspective, SoLo “just knows” who they are, as long as they are signed into the right Google or Apple account on the device. The rest of this post explains how we support that experience without giving up on account integrity or risk controls.

Another Common Journey: New Phone, Same Account

Another frequent pattern is when a member upgrades their phone or starts using SoLo on an additional device.

1. They install the SoLo app on the new phone.
2. On the login screen, they again tap “Continue with Google” or “Continue with Apple”.
3. They approve with the same device-level auth they already use.
4. They land in the same SoLo account, with their history and settings intact.

This matters because:

• Members do not need to remember how they originally signed up.
• They are less likely to create a duplicate account when switching devices.
• It reinforces the feeling that there is exactly one SoLo account attached to them.

From the outside, this looks simple: pick the familiar button and you are “back home”. Under the hood, the same identity and account rules apply regardless of which device they use.

High-Level Architecture

To keep the design portable and maintainable, you can split responsibilities across three layers that apply broadly to most stacks:

• Client (web / mobile)
  • Starts the OAuth flow when a user chooses Google or Apple
  • Handles redirects from providers via the auth service
  • Sends provider tokens or session references to the backend
• Auth service or managed auth provider
  • Manages OAuth redirects and token exchanges with Google and Apple
  • Normalizes identity data from providers into a stable shape
  • Issues a verifiable session or token for the backend to consume
• Application backend
  • Validates provider sessions via the auth service
  • Maps provider identities onto the internal account model
  • Enforces uniqueness, additional verification, and risk checks

Figure: High-level data flow for social sign in. The client delegates OAuth details to an auth service, which talks to providers and hands a verified identity to the application backend.

By keeping OAuth details in the auth service and identity logic in the backend, teams can:

• Add or remove providers without rewriting the core account model
• Reuse the same verification and risk controls regardless of login method
• Avoid leaking provider-specific assumptions into business logic

Identity Model: One User, Many Credentials

A key design choice is to model a single user entity as the source of truth, with multiple credentials attached to each account.

Conceptually:

• A user is the core identity in the system.
• Credentials are different ways a person can prove they are that user.
• Credentials include existing authentication methods plus social providers like Google and Apple.

Design principles that generalize well:

• The user record is canonical.
• Each credential links to exactly one user.
• Business rules determine when a new credential is created, merged into an existing user, or attached to an existing user via another signal like phone.

This separation keeps permissions, risk decisions, and product behavior independent from how a user logged in on a particular day.

In SoLo’s case, this “one user, many credentials” model fit naturally with how we already thought about members and accounts.

Guardrails That Keep Identity Models Safe

Introducing social sign in can accidentally weaken your identity model if there are no guardrails. A few practical principles help avoid that.

• Single source of truth for identity
  • Represent users with your own internal IDs.
  • Store provider identifiers only as credentials that point back to those IDs.
• Consistent account rules
  • Preserve existing uniqueness rules for phone and email.
  • Ensure social sign in never bypasses additional verification or risk checks.
• Provider-agnostic backend logic
  • Express backend logic in terms of generic “credentials from provider X” instead of tightly coupling to specific SDKs.
  • Let the auth service or managed provider own token formats and endpoints.
• Minimal exposure of secrets
  • Keep keys and secrets in secure server-side configuration or secret stores.
  • Ensure clients work with opaque, short-lived tokens only.

These constraints let teams evolve login UX without eroding the safety properties of their systems.

Build vs. Buy: Where To Draw The Line

It helps to think about social auth in two layers:

1. Raw OAuth and provider integrations
2. Application-specific identity and risk logic

For many teams, it makes sense to buy the first layer and build the second.

Why rely on a managed auth provider

• Standards move fast. OAuth and OpenID Connect evolve, and a dedicated provider can track changes and ship adjustments faster than most small teams.
• Multiple providers. You can start with Google and Apple and keep the door open for others without re-implementing flows.
• Operational maturity. Centralized handling of token lifecycles, refresh logic, outages, and security patches.

Why Keep Your Own Identity Layer

• Product consistency. Users see a single, coherent account model and recovery flow, whether they use phone, password, or social sign in.
• Risk and compliance. You can feed identity signals into your risk systems, logging, and audits without leaking internal detail to clients.
• Long-term flexibility. If you ever swap auth providers, your user model and authorization logic can remain largely unchanged.

This division of responsibilities tends to produce solutions that feel both safe and maintainable.

How This Helps SoLo, And Why It Might Help You

For SoLo Funds, the outcome of this work is straightforward:

• Members can get back to their accounts faster in the moments that matter.
• Our identity and risk model remains consistent and enforceable.
• Adding future providers is largely a configuration and mapping exercise.
• Since launch, we have seen a 6% increase in successful logins, and in the past week 31% of all logins have come through the new social sign in flow.

For other engineering teams, the concrete value is the pattern:

• Start from a durable user entity.
• Attach multiple credentials to that entity, including social providers.
• Define explicit rules for merging, attaching, and creating accounts.
• Keep OAuth details at the edge and business rules in your core.

Key Takeaways For Engineering Teams

• Model identity, not just UI flows. Treat social providers as credentials on a long-lived account model, not as separate accounts.
• Design explicit linking rules. Document when to merge by email, when to attach by phone or other signals, and when to create a new account.
• Keep providers at the edge. Use an auth service or managed auth provider for low-level OAuth, and keep your backend focused on mapping identities and enforcing business and risk rules.
• Avoid leaking implementation details. You can share architectures and patterns publicly without exposing code, topology, or secrets.

That is the balance we aimed for at SoLo Funds: a login experience that feels modern and low-friction for members, backed by an identity model that engineers can reason about and extend over time.

Written by Victor Ribeiro